Printing plates



April 25, 1955 A. J. ALBRECHT 2,706,947

PRINTING PLATES Filed July l. 1949 u J 2*]- ygwm y@ United States Patent Olilice 2,706,947 Patented Apr. 26, 1955 PRINTING PLATES Application July 1, 1949, serial No. 102,684 2 claims. (ci. lol- 4151) This invention relates to improvements in printing plates.

It is an object of the invention to provide a relief printing plate having the dimensions of stereotype plates i1 general use, but with improved characteristics of clear ness and durability and also having certain mechanical advantages, particularly in withstanding centrifugal and other forces tending to cause loosening or deformation of a plate during printing.

A further object of the invention is to provide a plate of the character indicated which may be fabricated with cheapness and rapidity comparable to stereotype plates as heretofore manufactured.

With these and other objects in mind, the invention consists 1n the combinations and arrangements of parts and will then be appended claims.

In the drawing:

Figure l is an end elevation, partly broken away, of a plate embodying the invention in a preferred form, and showing also a wrench employed in assembling the plate elements and fastening them together;

Figure 2 is an enlarged view of a portion of Figure l, and showing the parts in a different position;

Figures 3 and 4 are similar enlarged views showing sections through the plate of Figure 1 at different points along its edge; and

Figure 5 is a View 5 of Figure 2.

While the plate of the invention may be made in various dilferent sizes, as required, it will normally be of the general dimensions of a newspaper stereotype plate as now known, being semi-cylindrical in form and measuring approximately 22 inches circumferentially and approximately 17 inches along its straight edges. The plate comprises a back or dummy 1 of strong and rigid material such as steel or Duralumin to which is applied thc printing plate proper 2. The latter element takes the form of a magnesium alloy casting which may be about one-sixteenth inch thick. While the plate 2 is formed by a casting operation, as are conventional stereotype plates, improved clarity in the printing and also improved durability may be obtained by reason of the superior quality of the casting material as combined with ordinary type metal.

Since the specific gravity of the magnesium alloy and the thickness of the plate formed therefrom may both te of the order of a of the corresponding value for a conventional stereotype plate, the centrifugal force exerted on the plate during printing may be reduced to a value of the order of 1% of that encountered with plates of conventional construction. The plate will also possess superior qualities of resistance to growth through rolling action, such improved resistance being inherent in a thin plate. Since the dummy or backing plate 1 is utilized over and over again it may be carefully machined and made of the strongest, most rigid and most durable materials.

The plate 2 is formed with a groove or reduced section 3 running along both its ends and forming a slight shoulder or abutment 4 at the end of the plate. The groove 3 may reduce the thickness of the plate by about one-half. The dummy 1 is formed on one end with a rounded edge 5 and a slot 6 having an undercut groove 7, the plate 2 being slid endwise or axially into the dummy in a manner apparent from Figure 1. A bar l0 is formed with a similar slot 11 and groove 12, receiving the other end looking in the direction of the arrow of plate 2 and tits onto the other end of the dummy 1. This bar seats against the concave end 15 of the dummy 1 and is initially placed thereagainst in the position of Figure 2, but is rotatable for stretching the plate. The bar 10 is provided with a number of bores 16, at intervalsalong its length, for receiving pins 17 carried by a bar 18 to which is allixed a wrench handle 19. Turning the wrench from the position of Figure 2 to that of Figure l stretches the plate 2 around the dummy 1, the recesses 20 in the dummy accommodating the pins 17 of the wrench.

The bar 10, as shown in Figure 3, is provided with sockets 23 with slotted openings 24, at intervals along the bar. Ball headed screws 21 engage threaded bores 25 in the dummy and the plate is cut away forming slots as shown at 22 in Figure 5, to permit insertion and tightening of the screws 21, when the bar 10 has been turned to draw the plate taut about the dummy. The assembled dummy and printing plate may be fastened to a printing cylinder in any convenient manner by means of known clamping mechanisms, and its concave or inner surface or its curved edges may be slotted, beveled or otherwise suitably finished. The specific manner in which the dummy is held on a printing cylinder forms no part of the present invention and, accordingly, is not shown and described herein.

What is claimed is:

l. A composite printing plate comprising a semi-cylindrical rigid dummy of steel or the like material, means at the straight edges thereof for holding a printing plate on the dummy and a cast magnesium alloy printing plate about one-sixteenth inch thick, stretched and held around the dummy by the said plate holding means, the plate holding means for an edge of the plate comprising an axial slot and undercut groove in the dummy, the edge of the dummy adjacent the said slot having a smoothly curved surface leading from the cylindrical plate surface into the said slot, and the plate having a groove adjacent its edge, whereby the edge of the plate may be slid axially in and out of the slot and held therein against circumferential tension, the plate holding means for the other edge of the plate comprising a similarly slotted and grooved bar, rotatable on the edge of the dummy for stretching the plate around it, the bar having bores at intervals along its length to receive the pins of a wrench to turn the bar for stretching the plate on the dummy, and further bores at intervals along its length accommodating screws held in threaded bores in the dummy and fastening the bar to the dummy.

2. A device for supporting a thin printing plate for mounting on a printing cylinder, comprising a semi-cylinother straight edge of the dummy and rotatable for stretching a plate thereon, the bar being similarly slotted and grooved for holding the opposite edge of the plate, the bar having bores at intervals along its length for receiving the pins of a wrench for rotating the bar to stretch the plate, and further bores at intervals along its length to receive screws for fastening the bar to the dummy, the dummy also having threaded bores at corresponding intervals for holding the screws.

References Cited in the iile of this patent UNITED STATES PATENTS 

